Liquid separation device

ABSTRACT

A device for keeping liquids separate in a pipe, especially for use in a petroleum well, where the device comprises a diaphragm, which in its operative position and through use of pretensioned slats is stretched across the cross section of the pipe, and where each of the two end portions of the slats is connected to a boss, respectively, in a manner such that each the slats forms an outward bow relative to the common axis of the bosses, when in the neutral position.

RELATED APPLICATION

This application is the U.S. National Phase of PCT/NO02/00124 filed Mar.25, 2002 and claims priority to Norwegian Patent Application No.20011529 filed Mar. 26, 2001 and to Norwegian Patent Application No.20012867 filed Jun. 11, 2001, which are hereby incorporated by referenceherein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention regards a device, hereinafter termed a diaphragm bow,designed to segregate or separate liquids in a pipe, as is normally doneduring cementation work in a petroleum well, where use is often made ofliquids having different density, and where mixing of the liquids wouldcause the cementation to be totally or partially unsuccessful.

2. Description of Related Art.

A petroleum well in which a casting operation is to be carried out willordinarily contain drill fluid. When the grouting compound, which isslightly more viscous and has a higher density than drill fluid, isintroduced at the desired location in the well, there is a considerablerisk that the grouting compound may sink into the drill fluid and as aresult end up in the wrong place in the well. Another danger is that itwill be diluted by the drill fluid, and therefore not form asatisfactory casting.

This situation is well known to personnel working in this area, andseveral methods have been used to overcome the problem.

According to prior art, a relatively high viscosity liquid is duringcasting work in wells first pumped down to a location immediately belowthe location of the casting. The highly viscous liquid forms a verysluggish plug that will prevent the grouting compound subsequentlypumped into the well from moving downwards and mixing with the highlyviscous liquid or the drill fluid located underneath. In addition tobeing relatively costly, the method has proven not to worksatisfactorily.

When cementing in a liner, a bridge plug may be used. However bridgeplugs are not suitable for most of the cementation work that is relevantfor a petroleum well.

It is also known to arrange an inflatable plug at the casting location.Inflatable plugs have a much greater field of application than bridgeplugs, but have large physical dimensions and are therefore difficult totransport to the site by means of e.g. helicopter. Plugs of this typeare relatively costly.

A liquid separating means is described in Norwegian patent 303649,comprising two sets of slats, where each set of slats is fixed toseparate bosses connected to a common mandrel. Each set of slatsdistributed along the periphery of the device, and which at their freeend portions are braced against e.g. a pipe wall, are provided with acloth at these free end portions. The cloth is designed to cover thecross section of a pipe, thereby preventing liquids above and below thedevice from mixing. The device according to NO 303649 must be adapted toeach casting operation and introduced into the well while arranged inthe end portion of a lead-in pipe.

For all of the above mentioned methods, with the exception of the caseof using a high viscosity liquid, the lead-in pipe must be lowered intothe well just to position the liquid separating device. Often, therunning in is delayed due to limitations in the pumping capacity.

SUMMARY OF THE INVENTION.

The object of the invention is to remedy the disadvantages of prior art.

The object is achieved in accordance with the characteristics stated inthe description below and in the appended claims.

A diaphragm bow is formed with a number of bow slats, preferably evenlydistributed about the longitudinal axis of the diaphragm bow. The bowslats are designed to be resiliently braced in against the centralrodlike body of the diaphragm bow, so as to allow the device to bedisplaced through a pipe having a relatively small internal diameter.When the diaphragm bow reaches the site of use, thus leaving the lead-inpipe, the bow slats assume a braced position in which they abut theinside of a pipe that is to be filled with grouting compound, and whichhas a relatively large internal diameter. At least one circulardiaphragm/cloth is connected along its periphery to the bow slats,preferably at the central part of the bow slats, thus covering theinternal cross section of the relatively large pipe when the diaphragmbow is in the operative position. Experiments have shown that it ispossible to achieve satisfactory sealing action at a diameter ratio of1:10 between the lead-in pipe and the pipe to be sealed. In practice,this means that the diaphragm bow may be displaced down through a 50 mmpipe, then to expand in a manner so as to seal a 500 mm pipe againstmixing of liquids.

BRIEF DESCRIPTION OF THE DRAWINGS.

The following describes a non-limiting example of a preferred embodimentillustrated in the accompanying drawings, in which:

FIG. 1 shows a diaphragm bow according to the invention in the operativeposition in a pipe to be cemented;

FIG. 2 shows a section I—I in FIG. 1; and

FIG. 3 shows a diaphragm bow in a state of transport, on its way downthrough a lead-in pipe located in the pipe to be cemented, and where thelower end portion of the lead-in pipe is located at the cementing site.The figure only shows two of the slats.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT.

In the drawings, see FIGS. 1 and 2, reference number 1 denotes adiaphragm bow comprising a central rodlike mandrel 2, the lower endportion of which is rigidly mounted to a guiding body and at least onepacking 6, a boss 8 rigidly mounted to the mandrel 2, and a boss 10 thatmay travel along the mandrel 2.

A number of bow slats 12 are fixed between bosses 8 and 10, preferablydistributed in an even manner about the longitudinal axis of the mandrel2. The respective end portions of the bow slats 12 are rigidly mountedto the bosses 8 and 10 in a manner such as to assume an outward bowrelative to the body when in the neutral position. As an example, thebow slats 12 may be glued in bores 18 in the bosses 8 and 10. Thedirection of the bores 18 relative to the longitudinal axis of the rod 2and the radial direction of the bosses 8 and 10 is adjusted according tothe diameters the diaphragm bow 1 is to assume in the transport stateand in the operative state.

One or more circular diaphragms/cloths 14 having an external diameterslightly in excess of the internal diameter of a pipe 16 to be sealed,is connected to the central part of the bow slats 12, e.g. by means ofmetal wire or heat-shrinkable tubing.

When the diaphragm bow 1 is to be displaced down through a lead-in pipe20, see FIG. 3, the bow slats 12 are squeezed in towards the mandrel 2.When squeezed, the bow slats 12 experience resilient deformation neartheir mountings at the bosses 8 and 10, while the boss 10 is displacedout along the mandrel 2.

During the displacement of the diaphragm bow 1 in the lead-in pipe 20,the guiding body 4 causes the diaphragm bow 1 to steer out from e.g.pipe joints in the inside surface of the lead-in pipe 20. The packing 6is designed to seal in a sliding manner against the inside surface ofthe lead-in pipe 20. Thus the diaphragm bow 1 is suitable for beingpumped down through the lead-in pipe 20.

As the diaphragm bow 1 leaves the lead-in pipe 20, see FIG. 1, theresilient deformation forces in the bow slats 12 cause the travellingboss 10 to be displaced in the direction of the fixed boss 8, and thebow slats 12 assume their operative, bowed position, whereby thediaphragms 14 are stretched and seal across the internal cross sectionof the pipe 16.

The use of a diaphragm bow 1 according to the invention, where thediaphragm bow 1 is designed to be pumped down through a lead-in pipe 20in order then to open up so as to close off the cross section of thepipe 16, greatly simplifies cementing operations in petroleum wells.

1. A device for keeping liquids separate in a pipe, especially for usein a petroleum well, where the device comprises a diaphragm which in itsoperative position and through use of pretensioned slats is stretchedacross the cross section of the pipe, characterized in that each of thetwo end portions of the slats is connected to a boss, respectively, andwhere the slats are rigidly coupled to the boss such that the directionof a slat at the boss as viewed in the radial plane of the boss, exhibita non-zero angle with an imaginary radial line from the center of theboss to the point of engagement of that particular slat at the boss. 2.A device in accordance with claim 1, characterized in that the firstboss is rigidly mounted to a mandrel, to which mandrel the second bossis movably mounted.
 3. A device in accordance with claim 2,characterized in that the mandrel is equipped with at least one packing.4. A device in accordance with claim 2, characterized in that themandrel is equipped with a guiding body.
 5. A device in accordance withclaim 1, characterized in that the central part of the slats isconnected to at least one diaphragm.
 6. A device in accordance withclaim 1, characterized in that the slats are connected to the bosses bybeing glued into bores.